From: David Miller <davem@davemloft.net>
To: frank.blaschka@de.ibm.com
Cc: netdev@vger.kernel.org, linux-s390@vger.kernel.org
Subject: Re: [patch 2/2] [PATCH] qeth: l3 hw tx csum circumvent hw bug
Date: Sat, 15 Jan 2011 20:46:25 -0800 (PST) [thread overview]
Message-ID: <20110115.204625.226782089.davem@davemloft.net> (raw)
In-Reply-To: <20110113082359.GA11455@tuxmaker.boeblingen.de.ibm.com>
From: Frank Blaschka <frank.blaschka@de.ibm.com>
Date: Thu, 13 Jan 2011 09:23:59 +0100
> On Wed, Jan 12, 2011 at 11:47:35PM -0800, David Miller wrote:
>> From: frank.blaschka@de.ibm.com
>> Date: Thu, 13 Jan 2011 07:42:25 +0100
>>
>> > --- a/drivers/s390/net/qeth_l3_main.c
>> > +++ b/drivers/s390/net/qeth_l3_main.c
>> > @@ -2998,7 +2998,9 @@ static inline void qeth_l3_hdr_csum(stru
>> > */
>> > if (iph->protocol == IPPROTO_UDP)
>> > hdr->hdr.l3.ext_flags |= QETH_HDR_EXT_UDP;
>> > - hdr->hdr.l3.ext_flags |= QETH_HDR_EXT_CSUM_TRANSP_REQ;
>> > + hdr->hdr.l3.ext_flags |= QETH_HDR_EXT_CSUM_TRANSP_REQ |
>> > + QETH_HDR_EXT_CSUM_HDR_REQ;
>> > + iph->check = 0;
>> > if (card->options.performance_stats)
>> > card->perf_stats.tx_csum++;
>> > }
>>
>> You may not change the packet header contents blindly like this.
>> Otherwise unpredictable contents will be seen by tcpdump and any
>> other code path which has a clone of this packet.
>>
>> Thus, you'll need to guard this change with something like:
>>
>> if (skb_header_cloned(skb) &&
>> pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) {
>> dev_kfree_skb(skb);
>> goto tx_fail;
>> }
> Yes I know. Because of the suboptimal l3 driver design :-) we already have
> a private copy of the skb at this place. Thx!
I see, thanks for explaining.
Both patches applied, thanks.
prev parent reply other threads:[~2011-01-16 4:45 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-13 6:42 [patch 0/2] s390: qeth bug fixes for 2.6.38 next rc frank.blaschka
2011-01-13 6:42 ` [patch 1/2] [PATCH] qeth: postpone open till recovery is finished frank.blaschka
2011-01-13 6:42 ` [patch 2/2] [PATCH] qeth: l3 hw tx csum circumvent hw bug frank.blaschka
2011-01-13 7:47 ` David Miller
2011-01-13 8:23 ` Frank Blaschka
2011-01-16 4:46 ` David Miller [this message]
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